Methods For Atomic Layer Etching

ABSTRACT

Provided are methods of etching a substrate using atomic layer deposition apparatus. Atomic layer deposition apparatus including a gas distribution plate with a thermal element are discussed. The thermal element is capable of locally changing the temperature of a portion of the surface of the substrate to vaporize an etch layer deposited on the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. §120 of Ser. No.13/307,524, filed Nov. 30, 2011.

BACKGROUND

Embodiments of the invention generally relate to an apparatus and amethod for depositing materials. More specifically, embodiments of theinvention are directed to atomic layer deposition chambers with linearreciprocal motion.

In the field of semiconductor processing, flat-panel display processingor other electronic device processing, vapor deposition processes haveplayed an important role in depositing materials on substrates. As thegeometries of electronic devices continue to shrink and the density ofdevices continues to increase, the size and aspect ratio of the featuresare becoming more aggressive, e.g., feature sizes of 0.07 μm and aspectratios of 10 or greater. Accordingly, conformal deposition of materialsto form these devices is becoming increasingly important.

During an atomic layer deposition (ALD) process, reactant gases areintroduced into a process chamber containing a substrate. Generally, aregion of a substrate is contacted with a first reactant which isadsorbed onto the substrate surface. The substrate is then contactedwith a second reactant which reacts with the first reactant to form adeposited material. A purge gas may be introduced between the deliveryof each reactant gas to ensure that the only reactions that occur are onthe substrate surface.

There are many instances where the optimal reaction conditions for thefirst reactant are not the same as those of the second reactant. It isinefficient to change the temperature of the entire chamber andsubstrate between reactions. Additionally, some reaction conditions maycause long-term damage to the substrate and resulting device ifconditions are maintained for too long. Therefore, there is an ongoingneed in the art for improved apparatuses and methods of processingsubstrates by atomic layer deposition under more optimal reactionconditions.

SUMMARY

Embodiments of the invention are directed to methods of processing asubstrate. The substrate, in a processing chamber, is exposed to areactant gas at a first temperature to form an etch layer on a surfaceof the substrate. Unreacted reactant gas is removed from the processingchamber. The temperature of the substrate surface is elevated to asecond temperature to vaporize the etch layer from the substratesurface. The vaporized etch layer is removed from the processingchamber. The temperature of the substrate surface is decreased to aboutthe first temperature. In detailed embodiments, the first temperature isbelow an isotropic etch point of the etch layer.

In certain embodiments, the substrate is silicon. In specificembodiments, the reactant gas is fluorine. In detailed embodiments, thefirst temperature is in the range of about 20° C. to about 50° C. andthe second temperature is in the range of about 100° C. to about 200° C.

In some embodiments, exposing the substrate to the reactant gascomprises exposing the substrate to a combination of two or more gasesto form the etch layer. In detailed embodiments, the substrate has asilicon dioxide layer on the surface of the substrate and exposing thesubstrate to the reactant gas comprises exposing the substrate surfaceto one of water and ammonia followed by exposing the substrate tohydrofluoric acid. In specific embodiments, when water is used, thefirst temperature is about room temperature and the second temperatureis about 50° C. In certain embodiments, when ammonia is used, the firsttemperature is less than about 35° C. and the second temperature isabout 120° C.

Additional embodiments of the invention are directed to methods ofprocessing a substrate. The substrate having a surface is movedlaterally beneath a gas distribution plate comprising a plurality ofelongate gas ports including a first gas outlet to deliver a firstreactive gas. The first gas is delivered to the substrate surface toform an etch layer on the substrate surface. The temperature of thesubstrate surface is locally changed from a first temperature to asecond temperature, the second temperature being sufficient to vaporizethe etch layer. The substrate surface is purged of the vaporized etchlayer.

In detailed embodiments, the first temperature is below the isotropicetch point of the etch layer and the second temperature is greater thanor equal to the isotropic etch point of the etch layer. In specificembodiments, the substrate surface temperature is changed by one or moreof radiative heating or resistive heating.

In specific embodiments, the substrate is silicon and the first reactivegas comprises fluorine. In certain embodiments, the second temperatureis in the range of about 100° C. to about 200° C.

Further embodiments of the invention are directed to methods ofprocessing a substrate. The substrate having a surface is movedlaterally beneath a gas distribution plate comprising a plurality ofelongate gas ports including a first gas outlet to deliver a firstreactive gas and second gas outlet to deliver a second reactive gas. Thefirst reactive gas is delivered to the substrate surface to form a firstreactive layer on the substrate surface. The unreacted first reactivegas is purged. The second reactive gas is delivered to the substratesurface to react with the first reactive layer to form an etch layer onthe substrate surface. The unreacted second reactive gas is purged. Thetemperature of the substrate surface is locally changed from a firsttemperature to a second temperature, the second temperature beingsufficient to vaporize the etch layer. The substrate surface is purgedof the vaporized etch layer. In detailed embodiments, the firsttemperature is below the isotropic etch point of the etch layer and thesecond temperature is greater than or equal to the isotropic etch pointof the etch layer.

In some embodiments, the substrate surface temperature is changed by oneor more of radiative heating or resistive heating. In detailedembodiments, the substrate has a silicon oxide layer on the surface andthe first reactive gas is one of water and ammonia. In specificembodiments, the second reactive gas is hydrofluoric acid. In certainembodiments, the first temperature is less than about 50° C. and thesecond temperature is in the range of about 90° C. to about 130° C.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the inventionare attained and can be understood in detail, a more particulardescription of the invention, briefly summarized above, may be had byreference to the embodiments thereof which are illustrated in theappended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments of this invention and aretherefore not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

FIG. 1 shows a schematic cross-sectional view of an atomic layerdeposition chamber according to one or more embodiments of theinvention;

FIG. 2 shows a susceptor in accordance with one or more embodiments ofthe invention;

FIG. 3 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 4 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 5 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 6 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 7 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 8 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 9 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 10 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 11 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 12 shows a partial cross-sectional side view of an atomic layerdeposition chamber in accordance with one or more embodiments of theinvention;

FIG. 13 shows a reaction scheme in accordance with one or moreembodiments of the invention; and

FIG. 14 shows a reaction scheme in accordance with one or moreembodiments of the invention.

DETAILED DESCRIPTION

Embodiments of the invention are directed to atomic layer depositionapparatus and methods which provide improved processing of substrates.Specific embodiments of the invention are directed to atomic layerdeposition apparatuses (also called cyclical deposition) incorporatingat least one thermal element for changing the temperature of a portionof the substrate.

One or more embodiments of the invention are directed to methods ofetching a substrate or a material or layer from a substrate surface. Thesubstrate can be processed in any suitable processing chamber including,but not limited to, chemical vapor deposition chambers and atomic layerdeposition chambers. In the atomic layer deposition processes, eithertemporal or spatial separation of the reactant gases, purge gases andtemperature changes can be employed. Temporal separation is used todescribe a process by which the entire (or nearly entire) processingchamber is exposed to a single gas at a time with purge steps betweengases. Spatial separation is described in detail throughout andgenerally means that a first portion of the substrate is exposed to onereaction condition while a second portion of the substrate can besimultaneously exposed to a different reaction condition. Generally, asubstrate processed in a temporal scheme remains stationary, while oneprocessed in a spatial schema moves relative to the gas distributionplate.

In general, atomic layer etching process includes the steps of (1)introducing reactant A at a temperature below the isotropic etch pointonto a substrate (or targeted etch material); (2) pump purging thereactant away; (3) heat up the substrate to vaporize the by-product offthe substrate; (4) cool down the substrate to the temperature in step 1;and repeating steps 1 to 4 to the desired amount. The hardware maybenefit from easy and fast reactant introduction and removal. Oneexample is spatial separation of reactant, pump and purge gas channels.It may also be helpful to have fast and efficient heat and coolingcapabilities. Flash lamp, laser or light sources at specific wavelengthsranges or temperature controlled substrate holders can be used toachieve this.

It is known that molecular fluorine will not etch silicon at roomtemperature (unlike XeF₂). Molecular fluorine will start to etch if thesilicon temperature was heated up to about 100-200° C. In a spatialprocess, a substrate portion may be exposed to, for example, purge/pumpwith laser heating/purge/pump/fluorine/pump/purge/pump with laserheating/purge in a cyclic fashion. The heating can be laser or othersources as described and can be located in various positions.

Another example, generally related to etching silicon dioxide, involvesexposing the silicon dioxide surface to an HF/H₂O or HF/NH₃ environment.The spatial atomic layer deposition can be arranged so that portions ofthe substrate or surface are exposed to, sequentially, purge/pump/wateror ammonia/pump/purge/pump/HF/pump/purge/pump with heat source/purge.The wafer (substrate) will be exposed in this sequence: H₂O/HF/annealpump and repeat. For the water version, the substrate could be at roomtemperature and heat up may be as high as 50° C. For the ammoniaversion, the substrate could be at about 30° C. and heated up to about120° C.

In some embodiments, a substrate (or substrate surface) is exposed to areactant gas in a processing chamber. Exposure of the substrate surfaceto the reactant gas causes the formation of an etch film or etch layeron the surface of the substrate. As used in this specification and theappended claims, the terms “etch film” and “etch layer” are usedinterchangeably and refer to a film or layer on the surface of asubstrate, or a portion of the surface of a substrate, which can besubsequently stripped or removed from the surface. In detailedembodiments, the etch film or etch layer are removed from the surface ofthe substrate by substantially only increased temperature (orannealing). At this point, excess or unreacted reactant gas is purged orremoved from the processing chamber to avoid interference with anyadditional processes.

After the etch layer is formed on the substrate surface, the temperatureof the substrate (or substrate surface) is elevated from a firsttemperature to a second temperature. At the first temperature, the etchlayer is formed on the substrate surface. At the second temperature,however, the etch layer becomes vaporized, thus being removed from thesubstrate surface, leaving an etched surface. The vaporized etch layeris removed from the processing chamber to avoid deposition uponsubsequent lowering of the substrate temperature to the firsttemperature.

The first temperature is generally lower than the second temperature. Indetailed embodiments, the first temperature is below an isotropic etchpoint of the etch layer and the second temperature is about equal to orgreater than the isotropic etch point. As used in this specification andthe appended claims, the term “isotropic etch point” is defined as thelowest temperature that can vaporize the reaction by-product (i.e., theetch film).

There are multiple ways to change the temperature of the substratebetween the first temperature and the second temperature. In one or moreembodiments, the substrate or processing chamber is maintained at thefirst temperature and elevated to vaporize the etch layer. Thetemperature can be elevated at any point during or after the formationof the etch layer. In one or more embodiments, the temperature iselevated at substantially the same time as formation of the etch layer.In specific embodiments, the temperature is elevated after formation ofthe etch layer.

In some embodiments the substrate or processing chamber are maintainedat the second temperature and the reactive gas is held at the firsttemperature so that the gas is cool to temporarily lower the surfacetemperature of the substrate. After a short time, the temperature of thesubstrate surface would equilibrate with that of the processing chamber,thereby vaporizing the layer formed on the surface. The temperature ofthe substrate can be elevated by, for example, radiative, resistive orconductive heating or lowered by, for example, conductive cooling.

In one or more detailed embodiments, the substrate is silicon and thereactant gas is fluorine. The substrate is reacted with the fluorine gasat the first temperature in the range of about 20° C. and about 50° C.to form the etch layer. The substrate temperature is then raised to asecond temperature in the range of about 100° C. to about 200° C. tovaporize the etch layer from the surface of the substrate.

In some embodiments, exposing the substrate to the reactant gascomprises more than one step. For example, a combination of two or moregases may be necessary form the etch layer on the substrate surface.While this may require more than one individual gas exposure, it istermed a reactant gas herein because the ultimate conclusion is a etchlayer on the substrate. In certain embodiments, the substrate has asilicon dioxide layer on the surface and exposing the substrate to thereactant gas comprises exposing the substrate surface to one of waterand ammonia followed by exposing the substrate to hydrofluoric acid.When the substrate is first exposed to water, the first temperature isabout room temperature and the second temperature is about 50° C. Whenthe substrate is first exposed to ammonia, the first temperature is lessthan about 35° C. and the second temperature is about 120° C.

Etching using an atomic layer deposition type process can be useful,allowing for the integration of multiple processes within a singledeposition chamber. For example, it is possible to deposit the etchlayer at a temperature below the isotropic etch point and subsequentlyraise the temperature above this point. This is useful where there is anenergy barrier that must be overcome to etch a layer from the surface.Additionally, controlling the etching process in this manner may helpavoid spontaneous reactions and mitigate the risk of losing control ofthe etching process.

FIG. 1 is a schematic cross-sectional view of an spatial atomic layerdeposition system or system 100 in accordance with one or moreembodiments of the invention. The system 100 includes a load lockchamber 10 and a processing chamber 20. The processing chamber 20 isgenerally a sealable enclosure, which is operated under vacuum, or atleast low pressure. The processing chamber 20 is isolated from the loadlock chamber 10 by an isolation valve 15. The isolation valve 15 sealsthe processing chamber 20 from the load lock chamber 10 in a closedposition and allows a substrate 60 to be transferred from the load lockchamber 10 through the valve to the processing chamber 20 and vice versain an open position.

The system 100 includes a gas distribution plate 30 capable ofdistributing one or more gases across a substrate 60. The gasdistribution plate 30 can be any suitable distribution plate known tothose skilled in the art, and specific gas distribution plates describedshould not be taken as limiting the scope of the invention. The outputface of the gas distribution plate 30 faces the first surface 61 of thesubstrate 60.

Substrates for use with the embodiments of the invention can be anysuitable substrate. In detailed embodiments, the substrate is a rigid,discrete, generally planar substrate. As used in this specification andthe appended claims, the term “discrete” when referring to a substratemeans that the substrate has a fixed dimension. The substrate ofspecific embodiments is a semiconductor substrate, such as a 200 mm or300 mm diameter silicon substrate.

The gas distribution plate 30 comprises a plurality of gas portsconfigured to transmit one or more gas streams to the substrate 60 and aplurality of vacuum ports disposed between each gas port and configuredto transmit the gas streams out of the processing chamber 20. In thedetailed embodiment of FIG. 1, the gas distribution plate 30 comprises afirst precursor injector 120, a second precursor injector 130 and apurge gas injector 140. The injectors 120, 130, 140 may be controlled bya system computer (not shown), such as a mainframe, or by achamber-specific controller, such as a programmable logic controller.The precursor injector 120 is configured to inject a continuous (orpulse) stream of a reactive precursor of compound A into the processingchamber 20 through a plurality of gas ports 125. The precursor injector130 is configured to inject a continuous (or pulse) stream of a reactiveprecursor of compound B into the processing chamber 20 through aplurality of gas ports 135. The purge gas injector 140 is configured toinject a continuous (or pulse) stream of a non-reactive or purge gasinto the processing chamber 20 through a plurality of gas ports 145. Thepurge gas is configured to remove reactive material and reactiveby-products from the processing chamber 20. The purge gas is typicallyan inert gas, such as, nitrogen, argon and helium. Gas ports 145 aredisposed in between gas ports 125 and gas ports 135 so as to separatethe precursor of compound A from the precursor of compound B, therebyavoiding cross-contamination between the precursors.

In another aspect, a remote plasma source (not shown) may be connectedto the precursor injector 120 and the precursor injector 130 prior toinjecting the precursors into the processing chamber 20. The plasma ofreactive species may be generated by applying an electric field to acompound within the remote plasma source. Any power source that iscapable of activating the intended compounds may be used. For example,power sources using DC, radio frequency (RF), and microwave (MW) baseddischarge techniques may be used. If an RF power source is used, it canbe either capacitively or inductively coupled. The activation may alsobe generated by a thermally based technique, a gas breakdown technique,a high intensity light source (e.g., UV energy), or exposure to an x-raysource. Exemplary remote plasma sources are available from vendors suchas MKS Instruments, Inc. and Advanced Energy Industries, Inc.

The system 100 further includes a pumping system 150 connected to theprocessing chamber 20. The pumping system 150 is generally configured toevacuate the gas streams out of the processing chamber 20 through one ormore vacuum ports 155. The vacuum ports 155 are disposed between eachgas port so as to evacuate the gas streams out of the processing chamber20 after the gas streams react with the substrate surface and to furtherlimit cross-contamination between the precursors.

The system 100 includes a plurality of partitions 160 disposed on theprocessing chamber 20 between each port. A lower portion of eachpartition extends close to the first surface 61 of substrate 60, forexample, about 0.5 mm or greater from the first surface 61. In thismanner, the lower portions of the partitions 160 are separated from thesubstrate surface by a distance sufficient to allow the gas streams toflow around the lower portions toward the vacuum ports 155 after the gasstreams react with the substrate surface. Arrows 198 indicate thedirection of the gas streams. Since the partitions 160 operate as aphysical barrier to the gas streams, they also limit cross-contaminationbetween the precursors. The arrangement shown is merely illustrative andshould not be taken as limiting the scope of the invention. It will beunderstood by those skilled in the art that the gas distribution systemshown is merely one possible distribution system and the other types ofshowerheads and gas cushion plates may be employed.

In operation, a substrate 60 is delivered (e.g., by a robot) to the loadlock chamber 10 and is placed on a shuttle 65. After the isolation valve15 is opened, the shuttle 65 is moved along the track 70. Once theshuttle 65 enters in the processing chamber 20, the isolation valve 15closes, sealing the processing chamber 20. The shuttle 65 is then movedthrough the processing chamber 20 for processing. In one embodiment, theshuttle 65 is moved in a linear path through the chamber.

As the substrate 60 moves through the processing chamber 20, the firstsurface 61 of substrate 60 is repeatedly exposed to the precursor ofcompound A coming from gas ports 125 and the precursor of compound Bcoming from gas ports 135, with the purge gas coming from gas ports 145in between. Injection of the purge gas is designed to remove unreactedmaterial from the previous precursor prior to exposing the substratesurface 110 to the next precursor. After each exposure to the variousgas streams (e.g., the precursors or the purge gas), the gas streams areevacuated through the vacuum ports 155 by the pumping system 150. Sincea vacuum port may be disposed on both sides of each gas port, the gasstreams are evacuated through the vacuum ports 155 on both sides. Thus,the gas streams flow from the respective gas ports vertically downwardtoward the first surface 61 of the substrate 60, across the substratesurface 110 and around the lower portions of the partitions 160, andfinally upward toward the vacuum ports 155. In this manner, each gas maybe uniformly distributed across the substrate surface 110. Arrows 198indicate the direction of the gas flow. Substrate 60 may also be rotatedwhile being exposed to the various gas streams. Rotation of thesubstrate may be useful in preventing the formation of strips in theformed layers. Rotation of the substrate can be continuous or indiscreet steps.

Sufficient space is generally provided at the end of the processingchamber 20 so as to ensure complete exposure by the last gas port in theprocessing chamber 20. Once the substrate 60 reaches the end of theprocessing chamber 20 (i.e., the first surface 61 has completely beenexposed to every gas port in the processing chamber 20), the substrate60 returns back in a direction toward the load lock chamber 10. As thesubstrate 60 moves back toward the load lock chamber 10, the substratesurface may be exposed again to the precursor of compound A, the purgegas, and the precursor of compound B, in reverse order from the firstexposure.

The extent to which the substrate surface 110 is exposed to each gas maybe determined by, for example, the flow rates of each gas coming out ofthe gas port and the rate of movement of the substrate 60. In oneembodiment, the flow rates of each gas are configured so as not toremove adsorbed precursors from the substrate surface 110. The widthbetween each partition, the number of gas ports disposed on theprocessing chamber 20, and the number of times the substrate is passedback and forth may also determine the extent to which the substratesurface 110 is exposed to the various gases. Consequently, the quantityand quality of a deposited film may be optimized by varying theabove-referenced factors.

In another embodiment, the system 100 may include a precursor injector120 and a precursor injector 130, without a purge gas injector 140.Consequently, as the substrate 60 moves through the processing chamber20, the substrate surface 110 will be alternately exposed to theprecursor of compound A and the precursor of compound B, without beingexposed to purge gas in between.

The embodiment shown in FIG. 1 has the gas distribution plate 30 abovethe substrate. While the embodiments have been described and shown withrespect to this upright orientation, it will be understood that theinverted orientation is also possible. In that situation, the firstsurface 61 of the substrate 60 will face downward, while the gas flowstoward the substrate will be directed upward.

In yet another embodiment, the system 100 may be configured to process aplurality of substrates. In such an embodiment, the system 100 mayinclude a second load lock chamber (disposed at an opposite end of theload lock chamber 10) and a plurality of substrates 60. The substrates60 may be delivered to the load lock chamber 10 and retrieved from thesecond load lock chamber.

In some embodiments, the shuttle 65 is a susceptor 66 for carrying thesubstrate 60. Generally, the susceptor 66 is a carrier which helps toform a uniform temperature across the substrate. The susceptor 66 ismovable in both directions (left-to-right and right-to-left, relative tothe arrangement of FIG. 1) between the load lock chamber 10 and theprocessing chamber 20. The susceptor 66 has a top surface 67 forcarrying the substrate 60. The susceptor 66 may be a heated susceptor sothat the substrate 60 may be heated for processing. As an example, thesusceptor 66 may be heated by radiant heat lamps 90, a heating plate,resistive coils, or other heating devices, disposed underneath thesusceptor 66.

In still another embodiment, the top surface 67 of the susceptor 66includes a recess 68 configured to accept the substrate 60, as shown inFIG. 2. The susceptor 66 is generally thicker than the thickness of thesubstrate so that there is susceptor material beneath the substrate. Indetailed embodiments, the recess 68 is configured such that when thesubstrate 60 is disposed inside the recess 68, the first surface 61 ofsubstrate 60 is level with the top surface 67 of the susceptor 66.Stated differently, the recess 68 of some embodiments is configured suchthat when a substrate 60 is disposed therein, the first surface 61 ofthe substrate 60 does not protrude above the top surface 67 of thesusceptor 66.

In some embodiments, the substrate is thermally isolated from thecarrier to minimize heat losses. This can be done by any suitable means,including but not limited to, minimizing the surface contact area andusing low thermal conductance materials.

Substrates have an inherent thermal budget which is limited based onprevious processing done on the substrate. Therefore, it is useful tolimit the exposure of the substrate to large temperature variations toavoid exceeding this thermal budget, thereby damaging the previousprocessing. In some embodiments, the gas distribution plate 30 includesat least one thermal element 80 adapted to cause a local change intemperature at the surface of a portion of the substrate 60. The localchange in temperature affects primarily a portion of the surface of thesubstrate 60 without affecting the bulk temperature of the substrate.

Referring to FIG. 3, in operation, the substrate 60 moves relative tothe gas ports of the gas distribution plate 30, as shown by the arrow.The processing chamber 20, in this embodiment, may be held at a firsttemperature which is suitable for efficient reaction of precursor A withthe substrate 60, or layer on the substrate 60, but is too low forefficient reaction of precursor B. In the context of atomic layeretching, the first temperature may be below the isotropic etch point ofthe reaction product of precursor A (the etchant) and the substratesurface (or layer on the substrate surface). Region X moves past gasports with purge gases, vacuum ports and a first precursor A port, wherethe surface of the substrate 60 reacts with the first precursor A.Because the processing chamber 20 is held at a temperature suitable forthe precursor A reaction, as the substrate 60 moves to precursor B, theregion X is affected by the thermal element 80 and the local temperatureof region X is increased. In detailed embodiment, the local temperatureof region X is increased to a temperature which reaction of precursor Bis favorable. In the context of atomic layer etching, the localtemperature of region X can be increased to be about equal to or greaterthan the isotropic etch point of the etch film. Precursor B can be theetchant gas or can be replaced with an inert gas.

It will be understood by those skilled in the art that, as used anddescribed herein, region X is an artificially fixed point or region ofthe substrate. In actual use, the region X would be, literally, a movingtarget, as the substrate is moving adjacent the gas distribution plate30. For descriptive purposes, the region X shown is at a fixed pointduring processing of the substrate.

In detailed embodiments, the region X, which is also referred to as aportion of the substrate is limited in size. In some embodiments, theportion of the substrate effected by any individual thermal element isless than about 20% of the area of the substrate. In variousembodiments, the portion of the substrate effected by any individualthermal element is less than about 15%, 10%, 5% or 2% of the area of thesubstrate.

The thermal element 80 can any suitable temperature altering device andcan be positioned in many locations. Suitable examples of thermalelements 80 include, but are not limited to, radiative heaters (e.g.,lamps and lasers), resistive heaters, liquid controlled heat exchangersand cooling plates.

FIGS. 3-6 show various thermal element 80 placements and types. Itshould be understood that these examples are merely illustrative of someembodiments of the invention are should not be taken as limiting thescope of the invention. In some embodiments, the thermal element 80 ispositioned within at least one elongate gas port. Embodiments of thisvariety are shown in FIGS. 3-5. In FIG. 3, the thermal element 80 is aradiative heater positioned at an entrance to the gas port. Theradiative heater can be used to directly heat region X of the substrate60 as it passes adjacent to the gas port containing the radiativeheater. Here, the region X of the substrate is heated and changed whenthe region X is adjacent about gas port B.

It will be understood by those skilled in the art that there can be morethan one thermal element 80 in any given gas distribution plate 30. Anexample of this would be a gas distribution plate 30 with two repeatingunits of precursor A and precursor B. If the reaction temperature ofprecursor B is higher than precursor A, a thermal element may be placedwithin, or around/near each of the precursor B gas ports.

In specific embodiments, the radiative heater is a laser which isdirected along the gas port toward the surface of the substrate 60. Itcan be seen from FIG. 3 that as region X passes the thermal element, theelevated temperature remains for a period of time. The amount of timethat the temperature remains elevated for that region depends on anumber of factors. Accordingly, in some embodiments, the radiativeheater is positioned at one of the vacuum port or purge gas ports beforeprecursor B gas port. In these embodiments, region X maintains theresidual heat long enough to enhance reaction of precursor B. In theseembodiments, the region X is heated and the temperature changed in aregion extending from about gas port A to about gas port B.

FIGS. 4 and 5 show alternate embodiments of the invention in which thethermal element 80 is a resistive heater. The resistive heater can beany suitable heater known to those skilled in the art including, but notlimited to, tubular heaters. In FIG. 4, the resistive heater ispositioned within a gas port so that the gas passing the resistiveheater is heated. In specific embodiments, the gas passing the resistiveheater is heated to a temperature sufficient to provide efficientreaction with the substrate or layer on the substrate. The heated gaspassing the resistive heater can then heat the region X of thesubstrate. In this and similar embodiments, the region X of thesubstrate 60 surface temperature is changed when the region X atadjacent about gas port B.

FIG. 5 shows an alternate embodiment in which the resistive heater isplaced within a purge gas port. The placement of this resistive hater isafter the region X encounters precursor A and before it encountersprecursor B. Or in the case of atomic layer etching, the resistiveheater is placed after the region X is exposed to the etchant gas andprecursor B can be omitted or another etchant. The resistive heater ofthis embodiments heats the purge gas, which upon contact with thesubstrate, heats the portion, region X, of the substrate. In detailedembodiments, thermal element 80 is positioned such that the purge gas isheated or cooled prior to being flowed through the gas distributionplate.

Some embodiments similar to those of FIGS. 4 and 5 replace the resistiveheater with a cooling plate. The cooling plate can be placed within thegas flow in the gas ports to cool the temperature of the gas exitingthese ports. In some embodiments, the gas being cooled is one or more ofprecursor A or precursor B. In detailed embodiments, the thermal element80 is a cooling plate placed in a purge gas port to cool the purge gasto cool the temperature of the surface of the substrate. The coolingplate can be useful in the atomic layer etching processes as a means ofensuring that the temperature of region X is below the isotropic etchpoint of an etch layer to be formed by subsequent reaction.

FIG. 6 shows another embodiment of the invention in which the thermalelement 80 is positioned at a front face of the gas distribution plate30. The thermal element 80 is shown in a portion of the gas distributionplate which is between two gas ports. The size of this thermal elementcan be adjusted as necessary to minimize the gap between the adjacentgas ports. In specific embodiments, the thermal element has a size thatis about equal to the width of the partitions 160. The thermal element80 of these embodiments can be any suitable thermal element includingradiative and resistive heaters, or coolers. This particularconfiguration may be suitable for resistive heaters and cooling platesbecause of the proximity to the surface of the substrate 60. In detailedembodiments, the thermal element 80 is a resistive heater positioned ata front face of the gas distribution plate to directly heat the portion,region X, of the substrate 60. In specific embodiments, thermal element80 is a cooling plate positioned at a front face of the gas distributionplate to directly cool the portion, region X, of the substrate 60. Indetailed embodiments, the thermal element 80 is positioned on eitherside of a gas port. These embodiments are particularly suitable for usewith reciprocal motion processing where the substrate move back andforth adjacent the gas distribution plate 30.

In a detailed embodiment of FIG. 6, both precursor A and precursor B arethe same reactant gas. This reactant gas can be used to create an etchlayer on the substrate surface, or region X of the substrate surface.The etch layer can then be vaporized by the elevated temperatureresulting from exposure to the thermal element 80. The substrate, orregion X, can be exposed to the reactant gas multiple times before beingvaporized from the substrate. In various embodiments, the substratesurface is exposed to the etchant gas once, twice, three times, fourtimes or five times before the resultant etch layer is vaporized.

The thermal element 80 may be positioned before and/or after the gasdistribution plate 30. This embodiment is suitable for both reciprocalprocessing chambers in which the substrates moves back and forthadjacent the gas distribution plate, and in continuous (carousel orconveyer) architectures. In detailed embodiments the thermal element 80is a heat lamp. In the specific embodiment shown in FIG. 7, there aretwo thermal elements 80, one on either side of the gas distributionplate, so that in reciprocal type processing, the substrate 60 is heatedin both processing directions.

FIG. 8 shows another embodiment of the invention in which there are twogas distribution plates 30 with thermal elements 80 before, after andbetween each of the gas distribution plates 30. This embodiment is ofparticular use with reciprocal processing chambers as it allows for morelayers to be deposited in a single cycle (one pass back and forth).Because there is a thermal element 80 at the beginning and end of thegas distribution plates 30, the substrate 60 is affected by the thermalelement 80 before passing the gas distribution plate 30 in either theforward (e.g., left-to-right) or reverse (e.g., right-to-left) movement.It will be understood by those skilled in the art that the processingchamber 20 can have any number of gas distribution plates 30 withthermal elements 80 before and/or after each of the gas distributionplates 30 and the invention should not be limited to the embodimentsshown.

FIG. 9 shows another embodiment similar to that of FIG. 8 without thethermal element 80 after the last gas distribution plate 30. Embodimentsof this sort are of particular use with continuous processing, ratherthan reciprocal processing. For example, the processing chamber 20 maycontain any number of gas distribution plates 30 with a thermal element80 before each plate. Embodiments of this sort may also be particularlyuseful in atomic layer etching processes. The thermal element 80 beforeeach gas distribution plate can be used to ensure that the substratetemperature is below the isotropic etch point of an etch layer to beformed.

In some embodiments, the thermal element 80 is a gas distribution plate,or portion of a gas distribution plate, which is configured to direct astream of gas, which has been heated or cooled, toward the surface ofthe substrate. Additionally, the gas distribution plate can be heated orcooled so that proximity to the substrate can cause a change in thesubstrate surface temperature. For example, in a continuous processingenvironment, the processing chamber may have several gas distributionplates, or a single plate with a large number of gas ports. One or moreof the gas distribution plates (where there are more than one) or someof the gas ports can be configured to provide heated or cooled gas orradiant energy.

Additional embodiments of the invention are directed to methods ofprocessing a substrate. A substrate 60 is moved laterally adjacent a gasdistribution plate 30 comprising a plurality of elongate gas ports. Theelongate gas ports include a first gas port A to deliver a first gas anda second gas port B to deliver a second gas. The first gas is deliveredto the substrate surface and the second gas is delivered to thesubstrate surface. The local temperature of the substrate surface ischanged during processing. In some embodiments, the temperature ischanged locally after delivering the first gas to the substrate surfaceand before delivering the second gas to the substrate surface. Indetailed embodiments, the temperature is changed locally about the sametime as delivering the first gas or about the same time as deliveringthe second gas.

In detailed embodiments, the substrate surface temperature is directlychanged by one or more of radiative heating, resistive heating andcooling the substrate surface. In specific embodiments, the substratesurface temperature is indirectly changed by one or more of resistivelyheating and cooling one or more of the first gas and the second gas.

FIG. 10 shows an embodiment which may be of particular use in atomiclayer etching. A substrate 60 is laterally moved beneath the gasdistribution plate 30. A first gas (also referred to as an etchant gas,an etch gas, a precursor, etc.) is delivered to the surface of thesubstrate, or region X of the substrate, to form an etch layer. Thelocal temperature of the substrate, or region X, is changed from a firsttemperature to a second temperature using the thermal element 80.Elevating the temperature of the substrate surface (or a portion of thesubstrate surface, in the case of spatial processing) causes the etchfilm to be vaporized from the surface of the substrate. After the filmhas been etched, the vaporized etch film is removed from the processingchamber.

The embodiment shown in FIG. 10 includes two separate etchant gas portsfollowed by a thermal element 80. It will be understood by those skilledin the art that an additional pump port will be located downstream ofthe second thermal element 80 in order to ensure that the vaporized etchlayer is removed from the processing chamber. While two distinct etchantgas port/thermal element combinations are shown, any number can be used.In various embodiments, a single pass of the substrate beneath the gasdistribution plate results in at least one, two , three, four, five,six, seven, eight, nine or ten etch layer formation/vaporizationprocesses.

In the embodiment shown, the thermal element 80 provides heat to thesubstrate surface by heating the purge gas. It will be understood thatthe thermal element 80 can be, for example, a radiant heat sourcelocated in any or all of the pump or purge channels following theetchant gas. FIG. 11 shows an embodiment of the invention in which aradiant heat source (e.g., a laser) is positioned in the pump channeladjacent to and downstream of the etchant gas port. Again, there are twodistinct etch gas/thermal element 80 units shown, but it will beunderstood that this is merely one possible configuration and that otherconfigurations are within the scope of the invention. Positioning thethermal elements 80 in the pump (or vacuum) channels may be desirable asthe by-product created by vaporizing the film can be immediately removedfrom the chamber. This minimizes the potential for condensation of theby-product onto the substrate surface or a surface of the processingchamber.

FIG. 12 shows another detailed embodiment in which there are twodifferent thermal elements 80 a, 80 b used to elevate the temperatureand cool the temperature of the substrate, respectively. In thisembodiment, the region X, having a first temperature below the isotropicetch point of a layer to be formed, is first exposed to an etchant gasto form an etch layer on the substrate. The region X is then exposed toa pump channel with a radiant thermal element 80 a which elevates thetemperature of region X to equal to or greater than the isotropic etchpoint to vaporize the etch film from the substrate surface. Although theregion X is said to be “exposed to” the reactant gas, it will beunderstood that the reactant gas can be said to “contact” the region X.These phrases can be used interchangeably. The region X then is exposedto a purge gas which has been passed across a cooling thermal element 80b. The cooling thermal element 80 b can be any suitable cooler, forexample, a cold wire in the gas path. Between the purge gas and thecooling thermal element 80 b, the temperature of the substrate surfaceat region X is lowered below the isotropic etch point of the etch filmso that subsequent processing can occur.

FIG. 13 shows a detailed embodiment of the invention in which thesubstrate is silicon and the first reactive gas comprises fluorine. Thefluorine reacts with and deposits onto the silicon surface forming asilicon fluoride film. This reaction can take place at any suitablefirst temperature below the isotropic etch point. In variousembodiments, the first temperature is in the range of about 0° C. toabout 75° C., or in the range of about 10° C. to about 65° C., or in therange of about 20° C. to about 50° C., or in the range of about roomtemperature to about 45° C., or less than about 50° C., or less thanabout 40° C., or less than about 30° C. As used in this specificationand the appended claims, the term “room temperature” means a temperatureof about 25±2° C. Excess (i.e., unreacted) gases are pumped away fromthe surface of the substrate to avoid losing control of the etchprocess.

The temperature of the substrate (or a portion of the substrate) iselevated by any suitable means to a second temperature greater than theisotropic etch point of the silicon fluoride film. At this secondtemperature the silicon fluoride film is vaporized from the surface ofthe substrate resulting in a clean silicon surface and silicon fluoridespecies in the gas phase. In various embodiments, the second temperatureis in the range of about 80° C. to about 220° C., or in the range ofabout 100° C. to about 200° C., or greater than about 80° C., or greaterthan about 90° C, or greater than about 100° C., or greater than about120° C., or greater than about 140° C. The silicon fluoride species inthe gas phase are then removed from the processing chamber to avoidfurther reactions with the surface of the substrate upon cooling thesubstrate to the first temperature. In the spatial atomic layerdeposition schema, the gas phase etched layer can be pumped from thesurface of the substrate immediately after the thermal element heats theportion of the substrate.

Referring again to FIG. 6, another embodiment of the inventionincorporates at least two reactive gases to form the etch layer. Theprecursor A port can provide the first reactive gas to the substratesurface and the precursor B port can provide the second reactive gas tothe substrate surface. The first reactive gas and second reactive gasare used together to create the etch layer on the surface of thesubstrate. Elevating the temperature of the substrate then vaporizesthis etch layer.

FIG. 14 shows an example of this reaction schema in which the substrateis silicon and there is a silicon oxide layer on the surface of thesubstrate. The first reactive gas is delivered to the substrate surfaceto form a first reactive layer on the substrate surface. The firstreactive gas is shown as water, but can also be ammonia, as will beunderstood by those skilled in the art. The first reactive gas forms afirst reactive layer on the surface of the silicon oxide. Excess firstreactive gas is removed from the area of the surface of the substrate toavoid gas phase reactions in subsequent steps. The second reactive gas,shown as hydrofluoric acid, is flowed toward the substrate surface toreact with the first reactive layer on the substrate to form an etchlayer. The excess hydrofluoric acid is then pumped away from the surfaceof the substrate to avoid further reactions in subsequent steps. Thelocal temperature of the substrate surface is changed from a firsttemperature to a second temperature to vaporize the etch layer. Thevaporized etch layer is then pumped from the processing chamber.

In various embodiments, the first temperature is less than about 50° C.,or less than about 40° C., or less than about 30° C. In certainembodiments, the second temperature is in the range of about 90° C. toabout 130° C., or in the range of about 100° C. to about 125° C., or inthe range of about 100° C. to about 120° C.

Other etch reactions are contemplated and are within the scope of theinvention. For example germanium substrates can be etched with, forexample, hydrofluoric acid. This particular reaction is similar to thesilicon etching described but generally with higher temperatures. Carboncontaining materials can be etched with, for example, oxygen or ozone atdifferent temperatures. Additionally, carbon films and organic films canbe created and etched according to the described processes. Carbon andhydrocarbon or organic films can use O₂ or O₃ to etch at differenttemperatures. The optimal temperature will depend on the specificcompounds being used.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present invention without departing from the spirit andscope of the invention. Thus, it is intended that the present inventioninclude modifications and variations that are within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method of processing a substrate having asurface, the method comprising: laterally moving a surface beneath a gasdistribution plate comprising a plurality of elongate gas portsincluding a first gas outlet to deliver a first reactive gas; forming anetch layer on the substrate surface comprising exposing the substratesurface to the first reactive gas; locally changing a temperature of thesubstrate surface from a first temperature to a second temperature, thesecond temperature being sufficient to vaporize the etch layer; andlocally removing the vaporized etch layer from the surface, wherein at aportion of the surface is being exposed to the first reactive gas whilethe local temperature of a different portion of the surface is beingchanged.
 2. The method of claim 1, wherein the first temperature isbelow an isotropic etch point of the etch layer and the secondtemperature is greater than or equal to the isotropic etch point of theetch layer.
 3. The method of claim 1, wherein the surface temperature ischanged by one or more of radiative heating or resistive heating.
 4. Themethod of claim 1, wherein the surface comprises silicon.
 5. The methodof claim 4, wherein the first reactive gas comprises fluorine.
 6. Themethod of claim 5, wherein the first temperature is in the range ofabout 20° C. to about 50° C. and the second temperature is in the rangeof about 100° C. to about 200° C.
 7. The method of claim 1, whereinforming the etch layer on the substrate surface further comprisesexposing the substrate surface to a second reactive gas different fromthe first reactive gas.
 8. The method of claim 7, wherein one of thefirst reactive gas and the second reactive gas adsorb onto the surfaceand the other of the first reactive gas and the second reactive gasreact with the adsorbed reactive gas.
 9. The method of claim 1, whereinthe surface comprises a silicon dioxide layer and forming the etch layercomprises exposing the surface to one of water and ammonia followed byexposure to hydrofluoric acid.
 10. The method of claim 9, wherein whenwater is used, the first temperature is about room temperature and thesecond temperature is about 50° C.
 11. The method of claim 9, whereinwhen ammonia is used, the first temperature is less than about 35° C.and the second temperature is about 120° C.
 12. The method of claim 10,wherein the substrate is silicon and the first reactive gas comprisesfluorine.
 13. The method of claim 12, wherein the second temperature isin the range of about 100° C. to about 200° C.
 14. A method ofprocessing a substrate comprising: laterally moving a substrate having asurface beneath a gas distribution plate comprising a plurality ofelongate gas ports including a first gas outlet to deliver a firstreactive gas and second gas outlet to deliver a second reactive gas;delivering the first reactive gas to at least a portion of the substratesurface to form a first reactive layer on the substrate surface; locallyremoving unreacted first reactive gas; delivering the second reactivegas to at least a portion of the substrate surface having a firstreactive layer to react with the first reactive layer to form an etchlayer on the substrate surface; locally removing unreacted secondreactive gas; locally changing the temperature of the substrate surfacefrom a first temperature to a second temperature, the second temperaturebeing sufficient to vaporize the etch layer; and removing the vaporizedetch layer.
 15. The method of claim 14, wherein first temperature isbelow the isotropic etch point of the etch layer and the secondtemperature is greater than or equal to the isotropic etch point of theetch layer.
 16. The method of claim 14, wherein the substrate surfacetemperature is changed by one or more of radiative heating or resistiveheating.
 17. The method of claim 14, wherein the substrate has a siliconoxide layer on the surface and the first reactive gas is one of waterand ammonia.
 18. The method of claim 17, wherein the second reactive gasis hydrofluoric acid.
 19. The method of claim 18, wherein the firsttemperature is less than about 50° C. and the second temperature is inthe range of about 90° C. to about 130° C.